Lung ventilator system and method of ventilating lungs in breathing and non-breathing patients

ABSTRACT

A method of, or system for, ventilating lungs in breathing and non-breathing patients—including applications for anesthesia—may comprise maintaining an inspiratory flow rate at an inspiratory setpoint at a low flow setting. Lung pressure in a patient may be regulated between a high pressure setpoint and a low pressure setpoint with periodic expiratory flows and continuous inspiratory flow. An expiratory control valve may be adjusted to an open position when a lung pressure is at or above a high pressure setpoint. An expiratory control valve may be adjusted to a closed position when a lung pressure is at or below a low pressure setpoint. Concurrent venting outflow and CO 2  offloading through flow within the lungs may be facilitated by providing an intermittent expiratory flow to the patient while providing the continuous inspiratory flow.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of and claims priority toU.S. patent application Ser. No. 16/917,055, entitled “PatientVentilator Control Using Constant Flow and Breathing Triggers,” whichwas filed on Jun. 30, 2020 and issued as U.S. Pat. No. 10,980,954, thecontent of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure is directed to improved systems and methods ofventilating lungs in breathing and non-breathing patients, and maycomprise utilizing positive pressure to curate continuous gas flow andthus provide the needed oxygen when a patient cannot sufficiently andregularly self-inflate their lungs.

BACKGROUND

Acute Respiratory Distress Syndrome (ARDS) occurs in about 16% ofventilated adult patients in an intensive care unit (ICU) and can carrya mortality rate of up to 45%. In ARDS, a large percentage of the lungis collapsed. Aggressive therapy technologies, including high frequencyoscillating ventilation (HFOV) and airway pressure release ventilation(APRV), have not solved this issue. Neither can be used without concernfor negative sequelae. During general surgery, CT scans consistentlyshow dependent lung collapse within a few minutes after applyinganesthesia. Emerging science pertaining to the pathophysiology ofcovid-19 suggests that while some COVID patients do go into ARDS, otherssuffer from regional pulmonary vasoconstriction. This causes a lack ofblood flow to and from alveoli as compared to normal lung function.Traditional ARDSnet style ventilation, which is the default ICU method,has not shown benefit, and may create a compounding tamponade effect onpulmonary vasculature with covid-19 pathophysiology.

Improvements in ventilation are important. In 2016 the U.S. alone had5,534 hospitals, most have at least one ICU, many have 4-6 ICUsaccommodating 5-20 beds each. All of these hospitals need appropriatemethods of ventilating patients.

Typically, ARDS occurs 2.2 times per year per intensive care unit (ICU)bed. Further, it will occur in 16.1% percent in ventilated patients whoare admitted for more than 4 hours (per Brun, 2004) and despite currentmethods of ventilation there is still a mortality rate between 25% and43%. An analysis identifies underlying pathologic mechanisms,comorbidities, and population types. It is safe to say that the standardof care in mechanical ventilation, may itself contribute to a highfailure rate, and resultant deaths. These statistics ignore a potentialmorbidity among survivors who may suffer chronic and intractablefibrotic changes to their lung parenchyma. Indeed, the problem has notyet been solved.

SUMMARY

On opportunity exists for improved ventilation methods and systemsapplicable to ventilation applications, including anesthesia.Accordingly, in an aspect of the disclosure, a lung ventilator systemmay comprise an inspiratory tube configured to be disposed within apatient's airway tube as part of an inspiratory line, an inspiratoryflow rate measuring device coupled with the inspiratory line, and theinspiratory line coupled to a source of inspiratory air. An expiratoryline may be configured to be disposed at least partially within thepatient's airway tube, the expiratory line further comprising: anexpiratory flow rate measuring device and a lung pressure measuringdevice coupled with the expiratory line. An expiratory tube coupled tothe expiratory line, the expiatory tube disposed within the airway tube.An inspiratory airway may be positioned between the airway tube and theexpiratory tube, the inspiratory airway coupled to the inspiratory line.An inspiratory control valve may be operable for adjusting a rate ofinspiratory airflow through the inspiratory line to a patient lung. Anexpiratory control valve may be operable for adjusting a rate ofexpiratory airflow through the expiratory line away from the patientlung.

Particular embodiments of the lung ventilator system may furthercomprise a ventilatory controller operable to provide continuousinspiratory flow through the inspiratory line while providing anintermittent expiratory flow from the patient through the expiratorytube while providing the continuous inspiratory flow to facilitateconcurrent venting outflow. An ETCO₂ sensor may be disposed within theexpiratory line. The expiratory tube may extend below a lower end of theairway tube. The airway tube may further comprise an endotracheal tubeor a tracheostomy tube.

According to an aspect of the disclosure, a method of ventilating lungsin breathing and non-breathing patients may comprise maintaining aninspiratory flow rate at an inspiratory setpoint at a low flow setting.Lung pressure may be regulated in a patient between a high pressuresetpoint and a low pressure setpoint with periodic expiratory flows andcontinuous inspiratory flow by: adjusting an expiratory control valve toan open position when a lung pressure is at or above a high pressuresetpoint, and adjusting an expiratory control valve to a closed positionwhen a lung pressure is at or below a low pressure setpoint.

According to an aspect of the disclosure, a method of ventilating lungsin breathing and non-breathing patients may comprise providingcontinuous inspiratory flow to a patient, and providing an intermittentexpiratory flow from the patient while providing the continuousinspiratory flow to facilitate concurrent venting outflow and CO₂offloading from the lung.

Particular embodiments of the method of ventilating lungs in breathingand non-breathing patients may further comprise providing additionalflow through the lung in response to a trigger resulting from apatient's attempt to initiate a spontaneous breath. The trigger for aspontaneous breath comprising a drop of pressure, or a spontaneousincrease of flow, brought about by contracture of the patient'sdiaphragm. The trigger for expiratory flow may comprise one or more of:(i) an increase of pressure, (ii) real time continuous ETCO₂ readings ina range of 30-70 mm of mercury (Hg), or (iii) after a defined time delaygreater than 1.5 seconds. The trigger for expiratory flow comprisesreadings from an ETCO₂ sensor of 30-70 mm of mercury (Hg), wherein theETCO₂ may comprise reading a real-time result produced by constantmonitoring with a slight continuous expiratory flow sufficient forobtaining a reading from the ETCO₂ sensor, and wherein the inspiratoryflow is upregulated to compensate for the slight continuous expiratoryflow. A spontaneous breath control may be regulated by detecting apredetermined pressure drop in lung pressure when the expiatory controlvalve is substantially closed, and triggering an inspiratory setpointcycle after detecting the predetermined pressure drop. Triggering theinspiratory setpoint cycle may comprise changing the inspiratorysetpoint to a high flow setting to increase inspiratory flow, andsubsequently changing the inspiratory setpoint to a low flow settingafter increasing the inspiratory flow once lung pressure is at or abovea spontaneous breath pressure setpoint.

Particular embodiments of the method of ventilating lungs in breathingand non-breathing patients may further comprise the low flow settingcomprising a flow in a range of 30-350 ml/second. The inspiratory flowmay comprise a low flow setting comprising a flow in a range of 30-350ml/second. The high pressure setpoint may be within a range of 8-55centimeters of H₂O. The method may further comprise regulating lungpressure in a patient between a high pressure setpoint and a lowpressure setpoint, the high pressure setpoint being in a range of 8-55centimeters of H₂O. The low pressure setpoint may be within a range of3-35 centimeters of H₂O. Lung pressure in a patient may be regulatedbetween a high pressure setpoint and a low pressure setpoint, the lowpressure setpoint being in a range of 3-35 centimeters of H₂O. Thepredetermined pressure drop may be in a range of 0.5-3 centimeters ofH₂O for a time in a range of 0.2-4 seconds.

Particular embodiments of the method of ventilating lungs in breathingand non-breathing patients may further comprise: (i) measuring anexpiratory ETCO₂ amount with an ETCO₂ measurement device, (ii) furtheropening the expiratory control valve when the expiratory ETCO₂ amount isabove an ETCO₂ high setpoint to control the expiratory flow according tothe low flow setting, and (iii) substantially closing the expiratorycontrol valve when the ETCO₂ amount is at or below an ETCO₂ low setpointwhile the lung pressure is at or below the low pressure set point. Themethod may also further comprise: (i) measuring an expiratory ETCO₂amount with an ETCO₂ measurement device, further opening the expiratorycontrol valve when the expiratory ETCO₂ amount is above an ETCO₂ highsetpoint of 30-70 mm of mercury (Hg) to control the expiratory flowaccording to the low flow setting, and substantially closing theexpiratory control valve when the ETCO₂ amount is at or below an ETCO₂low setpoint 20-50 mm of mercury (Hg) while the lung pressure is at orbelow the low pressure set point. At least a 5 mm mercury (Hg) offsetbetween the high setpoint and the low setpoint may be maintained.

The foregoing and other aspects, features, applications, and advantageswill be apparent to those of ordinary skill in the art from thespecification, drawings, and the claims. Unless specifically noted, itis intended that the words and phrases in the specification and theclaims be given their plain, ordinary, and accustomed meaning to thoseof ordinary skill in the applicable arts. The inventors are fully awarethat he can be his own lexicographer if desired. The inventors expresslyelect, as their own lexicographers, to use only the plain and ordinarymeaning of terms in the specification and claims unless they clearlystate otherwise and then further, expressly set forth the “special”definition of that term and explain how it differs from the plain andordinary meaning. Absent such clear statements of intent to apply a“special” definition, it is the inventors' intent and desire that thesimple, plain and ordinary meaning to the terms be applied to theinterpretation of the specification and claims.

The inventors are also aware of the normal precepts of English grammar.Thus, if a noun, term, or phrase is intended to be furthercharacterized, specified, or narrowed in some way, then such noun, term,or phrase will expressly include additional adjectives, descriptiveterms, or other modifiers in accordance with the normal precepts ofEnglish grammar. Absent the use of such adjectives, descriptive terms,or modifiers, it is the intent that such nouns, terms, or phrases begiven their plain, and ordinary English meaning to those skilled in theapplicable arts as set forth above.

Further, the inventors are fully informed of the standards andapplication of the special provisions of 35 U.S.C. § 112(f). Thus, theuse of the words “function,” “means” or “step” in the DetailedDescription or Description of the Drawings or claims is not intended tosomehow indicate a desire to invoke the special provisions of 35 U.S.C.§ 112(f), to define the invention. To the contrary, if the provisions of35 U.S.C. § 112(f) are sought to be invoked to define the inventions,the claims will specifically and expressly state the exact phrases“means for” or “step for”, and will also recite the word “function”(i.e., will state “means for performing the function of [insertfunction]”), without also reciting in such phrases any structure,material or act in support of the function. Thus, even when the claimsrecite a “means for performing the function of . . . ” or “step forperforming the function of . . . ,” if the claims also recite anystructure, material or acts in support of that means or step, or thatperform the recited function, then it is the clear intention of theinventors not to invoke the provisions of 35 U.S.C. § 112(f). Moreover,even if the provisions of 35 U.S.C. § 112(f) are invoked to define theclaimed aspects, it is intended that these aspects not be limited onlyto the specific structure, material or acts that are described in thepreferred embodiments, but in addition, include any and all structures,materials or acts that perform the claimed function as described inalternative embodiments or forms of the disclosure, or that are wellknown present or later-developed, equivalent structures, material oracts for performing the claimed function.

The foregoing and other aspects, features, and advantages will beapparent to those of ordinary skill in the art from the specification,drawings, and the claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 shows an illustration of ventilating tubes when installed in theairway of a patient.

FIGS. 2A-2B show cross sections of the endotracheal tube in twolocations.

FIG. 3A shows a preferred ventilating tube arrangement in the airway ofa patient.

FIGS. 3B-3H show exemplary inspiratory and expiratory tube arrangementsand connectors.

FIG. 3I shows an embodied use of a tracheostomy tube.

FIG. 4A-4B show the equipment used to control ventilation in the patentalong with an XY sensor.

FIG. 5 shows a typical display and control interface for the newbiomimetic flow based pressure limited ventilation mode.

FIG. 6A-6D show graphs of lung pressure and flow for a breathingpatient, and for a continuous ventilatory flow without spontaneousbreathing.

FIG. 7 shows a Capnographic Waveform for a typical breathing patient andfor a constant inspiratory flow.

DETAILED DESCRIPTION

The present disclosure includes one or more aspects or embodiments inthe following description with reference to the figures, in which likenumerals represent the same or similar elements. Those skilled in theart will appreciate that the description is intended to coveralternatives, modifications, and equivalents as may be included withinthe spirit and scope of the disclosure as defined by the appended claimsand their equivalents as supported by the following disclosure anddrawings. In the description, numerous specific details are set forth,such as specific configurations, compositions, and processes, etc., inorder to provide a thorough understanding of the disclosure. In otherinstances, well-known processes and manufacturing techniques have notbeen described in particular detail in order to not unnecessarilyobscure the disclosure. Furthermore, the various embodiments shown inthe figures are illustrative representations and are not necessarilydrawn to scale.

This disclosure, its aspects and implementations, are not limited to thespecific equipment, material types, or other system component examples,or methods disclosed herein. Many additional components, manufacturingand assembly procedures known in the art consistent with manufacture andpackaging are contemplated for use with particular implementations fromthis disclosure. Accordingly, for example, although particularimplementations are disclosed, such implementations and implementingcomponents may comprise any components, models, types, materials,versions, quantities, and/or the like as is known in the art for suchsystems and implementing components, consistent with the intendedoperation.

The word “exemplary,” “example,” or various forms thereof are usedherein to mean serving as an example, instance, or illustration. Anyaspect or design described herein as “exemplary” or as an “example” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs. Furthermore, examples are provided solely forpurposes of clarity and understanding and are not meant to limit orrestrict the disclosed subject matter or relevant portions of thisdisclosure in any manner. It is to be appreciated that a myriad ofadditional or alternate examples of varying scope could have beenpresented, but have been omitted for purposes of brevity.

Where the following examples, embodiments and implementations referenceexamples, it should be understood by those of ordinary skill in the artthat other manufacturing devices and examples could be intermixed orsubstituted with those provided. In places where the description aboverefers to particular embodiments, it should be readily apparent that anumber of modifications may be made without departing from the spiritthereof and that these embodiments and implementations may be applied toother technologies as well. Accordingly, the disclosed subject matter isintended to embrace all such alterations, modifications and variationsthat fall within the spirit and scope of the disclosure and theknowledge of one of ordinary skill in the art.

All amounts, ratios, and percentages are by weight unless otherwiseindicated. The articles “a”, “an”, and “the” each refer to one or more,unless otherwise indicated by the context of the specification. Thedisclosure of ranges includes the range itself and also anythingsubsumed therein, as well as endpoints. For example, disclosure of arange of 2.0 to 4.0 includes not only the range of 2.0 to 4.0, but also2.1, 2.3, 3.4, 3.5, and 4.0 individually, as well as any other numbersubsumed in the range. Furthermore, disclosure of a range of, forexample, 2.0 to 4.0 includes the subsets of, for example, 2.1 to 3.5,2.3 to 3.4, 2.6 to 3.7, and 3.8 to 4.0, as well as any other subsetsubsumed in the range. Similarly, the disclosure of Markush groupsincludes the entire group and also any individual members and subgroupssubsumed therein.

The disclosure describes a new inspiration/expiration flow design thatis a biomimetic flow-based mode, which may comprise expiratory flowsprimarily created by lung pressure set points. The disclosure and themethods, systems, and devices described herein reflect an approach, andthe philosophy, of biomimicry. Biomimicry is the design and productionof materials, structures, and systems that are modeled on biologicalentities and processes. It is a rigorous, nonlinear innovationmethodology, where nature's principles are used to sustainably meetchallenges of design, engineering, ethics, and process. It can beutilized to solve and resolve issues related to lung function andventilation problems.

The improved flow can provide a gentler ventilatory mode to the settingof the pathophysiology described in the Background. It avoids orseverely limits barotrauma, volutrauma, atelectrauma and, extremes ofarterial CO₂ when compared to existing ventilators. This mode ispossible by using a new multi-tube airway inserted into a patient'sendotracheal tube. The new airway system allows a continuous inspiratoryflow along with periodic concurrent expiratory flows. Both flows arecompliance dependent and pressure responsive, and avoid previousdifficulties seen with other modes of mechanical ventilation. This modemay be enabled by using a new dual lumen tube inserted into a patientTrachea. Additionally, the control provides support for patientinitiated breathing which is initiated by a lung pressure drop. Thiscontrol provides continuous and gentle recruitment of lung alveoli.

Basic Ventilatory Mechanics, Modes, Physiology, and Related Context

This disclosure provides an improved method of ventilating lungs, usinga novel default mode which offers continuous inspiratory flow (inflationvia positive pressure ventilation) with intermittent concurrentexpiratory flow (passive exhalation). In contrast to traditionalventilatory modes, where inspiration and exhalation must occur only atseparate times without temporal overlap and so can never occur togetherbut only in sequence, this modeseeks to offer continuous gentlerecruitment (opening up) of functional anatomical lung units (alveoli).

Ventilation is the movement of gases into and out of the lungs; and assuch is a broader term than respiration, where respiration includes boththe movement of gasses and further includes movement of gasses across abarrier. When terrestrial mammals, including humans, are in a healthystate, breathing is the result of autonomic mechanismsor consciousintent. Either way, a diaphragm contraction is triggered which leads tolargercavity size in the chest. This results in a low lung pressure ascompared to atmospheric pressure. This allows air to flow into the lungsand is called “negative pressure ventilation.”

When the diaphragm then relaxes, it does so in a direction whichdecreases the volume of the chest back to the previous baseline. Thisincreases the intrathoracic pressure above atmospheric pressure andexhalation results. Terrestrial mammals breathe based on tidalventilation. Tidal volume times breaths per minute yields minuteventilation (amount of air moved in a minute).

Respiration is a process of molecular exchange, largely by diffusion,which occurs at the alveolar-capillary bed level (e.g. O₂ rich gasmixtures go in, metabolism occurs, and CO₂ rich gas mixtures becomeavailable for exhalation). The normal partial pressure of CO₂ in humanarterial blood (PaCO₂) is 35-45 mmHg. Without sufficient ventilation andrespiration both atelectasis (alveolar collapse) and acidosis secondaryto CO₂ build-up (hypercapnia [PaCO₂>45 mmHg]) occur. Carbon dioxide cantherefore be thought of as a source of acid in humans:([CO₂+H₂O]→H₂CO₂→[HCO²⁻+H+]). The normal pH range for humans is7.35-7.45 and a pH <7.2 is associated with grave disease states andmetabolic dysfunction as many common metabolic reactions, includingthose involving vasoactive agents such as epinephrine and noradrenaline,are negatively impacted.

Positive pressure ventilation (PPV) is the basis for most existingventilators. Today, mechanically ventilated patients usually havesingle-lumen airway tubes inserted into their tracheas through which airis moved in a closed circuit (ventilator, tube, bronchi, and lungs). Intidal ventilation, that is a sequence of inspiration and exhalationwithout temporal overlap of the two. PPV is accomplished when thepressure generated by a ventilator exceeds the pressure in the lungsthus causing inspiratory airflow and resultant inflation of the lungs.When positive pressure is stopped, the lungs naturally recoil and startto collapse until they reach an internal pressure state equal to that ofthe ventilator circuit. Depending on the ventilator mode, levels ofsedation, and the patient's innate state, a given patient may be eitherapneic without the ventilator's help or may breathe spontaneously, basedon diaphragmatic movement, in addition to ventilator-initiated breaths.Most modern ventilation systems detect pressure changes that come fromdiaphragmatic motion and then initiate a breath based on such “demand”by the patient in addition to other breaths they are set to give. Suchpositive pressure in addition to negative pressure generated by thepatient helps the patient overcome resistance inherent in the ventilatorcircuit relative to ambient air.

Flow, in the setting of positive pressure mechanical ventilation, is therate at which gases are pushed into the lung. Breath volume, rate, lungcompliance (i.e. distensibility and elastic recoil [Cdyn=tidal volume/APressure]) and inspiratory phase duration all impact flow. Cycle time inventilation can be determined by dividing the seconds per minute by thebreaths per minute. For example, at a rate of 12 breaths per minute, 5seconds are allotted for each breath, which includes both theinspiratory and expiratory phases, whereas at a rate of 30, only 2seconds would be allotted per breath. Flow per unit time can, therefore,be calculated if the volume per breath and the duration of theinspiratory phase are known. For example, with 600 ml/breath and aninspiratory phase of one second, the flow rate is 600 ml/sec; whereas at600 ml/breath with an inspiratory time of 3 seconds, the flow rate is200 ml/sec.

Air takes the path of least resistance in filling a lung, usually intoopen air passages and open sacs (recruited alveoli). To re-open, orrecruit, an atelectatic alveolus, one must ventilate it such that a“critical opening pressure” is exceeded. The analog of a balloon may bea useful illustration. When one blows up a balloon, a little bit of airenters with very little pressure, but soon, much more pressure is neededto overcome a threshold after which the balloon inflates towards maximumwith relative ease. It is similar with the alveolus. If openingpressures are continuously exceeded, alveolar segments will berecruited. When pressures drop below opening thresholds for extendedperiods, without sufficient residual aeration, atelectasis can result.

When inspiratory duration to volume ratios (Id:V) are low (i.e. shorttimes and larger volumes) flow rates are higher than when Id:V ratiosare lower. When flow rates are higher, gas distribution within the lungis more heterogeneous with gas moving to already aerated areas morereadily, resulting in local over distension and volutrauma, while otherregions remain poorly aerated. This problem is exacerbated in diseasestates. When flow rates are lower a more homogenous distribution ofgases can be observed throughout the lungs with a concurrent increase inthe removal of CO₂ at a given metabolic rate and minute volume. Thus,the curation of a low-flow state in the setting of sufficient minutevolume can be beneficial as it minimizes volutrauma, mitigateshypercapnic acidosis, and promotes aeration.

Positive end expiratory pressure (PEEP) is the result of incomplete lungemptying. In healthy states the lungs do retain some residual volume onend expiration, and that volume yields some pressure. This pressure hasa stenting effect such that more alveolar units which were already open,remain so, as compared to states without PEEP when expiration occurs.Normal physiologic PEEP in humans is the subject of some debate, butcurrent thinking is that it is in the range of 3-5 cm of H₂O. PEEPitself, however, does not expand alveolar segments. Mean airway pressure(PAW) is a time-average pressure accounting for both peak inspiratorypressure (PIP) and PEEP. As long as PAW exceeds critical openingpressures and there is positive airflow, recruitment will occur. PAW canbe calculated as follows: (PIP×inspiratory units [time]+PEEP×expiratoryunits [time])/total number of units=PAW). (As an example for I: Eat 1:2PEEP at 5, PIP at 20:(20+5+5)/3=10 and I:E 4:1 PIP 20 PEEP5:(20×4+5)/5=17). Recruitment is achieved by peak and mean airwaypressures which exceed the critical opening pressures of collapsedalveoli. PEEP is important for maintaining recruitment.

Gas Flow in Brief

In a lung, air flows from regions of higher pressure to regions of lowerpressure at rates which can be predicted based on the pressures,volumes, tube diameters, reservoir capacities and measures ofdistensibility and elasticity, as well as the types of flows involved.Laminar flow is smooth and unidirectional, whereas turbulent flow, whichoften occurs as gasses bounce off boundary layers, involves many morelocal variances in flow and is less efficient. This can be expressed bythe Reynold's number, where Re<2000=Laminar Flow, Re2000-4000=transitional, Re>4000=turbulence. In general, lower flow rateshave a lower Reynolds number and reduce the turbulence of flow.

When air flows at higher velocities, especially through an airway withirregular walls, flow is turbulent, and tends to form eddies. This isfound mainly in the largest airways, like the trachea. It is expectedthat flow though smooth airway tubes will be mostly laminar with somepossible turbulence at the ends of the tubes as gas is forced into alarger area of relatively lower pressure. Further, gas under pressurewill push through small diameter airway tubes more readily than thelungs into which they are inserted. Large amounts of air can flowthrough relative choke points. While in a lung, the air flow can remaincontinual and at a predictable and even rate. The common thinking offlow per minute is erroneous, as breaths take less than a minute andflow is not evenly distributed over long timespans in traditionalventilatory modes. Thus, a tendency for the person of ordinary skill inthe art (POSA) to not think in terms of flow/sec can make it difficultand non-obvious for a POSA, ventilator operator, or designers toappreciate the advantages and approaches described herein. In a clinicalsetting, obtaining a continuous low-flow/sec state advantageously avoidsreginal over distension and achieve a homogeneous gas distribution.

Acute Respiratory Distress Syndrome (ARDS)—Pathological Basis, andAttempts at Mitigation

Generally, ventilation problems can be defined as either outflowobstruction (such as in emphysema and asthma), or restrictive, where thelungs are hard to inflate (such as in fibrotic processes or cases ofcircumferential burns to the trunk which yield a tightening of the skinpreventing chest wall excursion).

Three types of ventilator induced lung injury have been well documented:

-   -   1. barotrauma (injury from too much pressure),    -   2. volutrauma (injury owing to overstretching with too much        volume per vent breath, which has been shown to cause        inflammatory cytokine release), and    -   3. atelectrauma (sheer force injury from collapse and repeated        re-expansion of the alveoli). Safe “recruitment” is the        re-expansion and maintenance of (non-injurious) inflation of        alveolar units previously collapsed (atelectatic) by disease        processes.

Two basic types of ventilation have historically been undertaken. Thefirst, volume control, occurs when the user sets a volume which resultsin the generation of sufficient pressure to fill the lung. This canresult in barotrauma if the lung is stiff. The second main category ofventilation is termed “pressure control.” In pressure control modes, adriving pressure is set and, depending on the compliance of the lung, asmeasured, amount of air flows in as a result until the set pressure isreached. With stiff lungs, this can result in hypoventilation,hypercapnia and acidosis. When lungs that are improving, but withunmonitored compliance, such a mode can yield volutrauma.

ARDS is a well-documented syndrome with myriad contributing pathologiccauses. Historically, ARDS is defined, whatever the cause(s) for aparticular patient, by a poor partial pressure of oxygen in arterialblood (PaO₂) to fraction of inspired oxygen (FiO₂) ratio (P:F). Thisfalls into the restrictive lung disease category. Typically, complianceis poor, and many lung regions are profoundly hypoventilated showing a“ground-glass” appearance on an x-ray. If such a patient is ventilatedwith normal volumes, and the lungs are stiff, CO₂ elimination is low andventilator induced lung injury (VILI) in the forms of volutrauma,atelectrauma, and barotrauma can result.

In ARDS, it is known that a system of dynamic disequilibrium exists suchthat whatever lung segment is made dependent (down) will become thehardest to aerate.

In response to these problems, several responses have been tried.

Gattinoni (2005) proposed the idea of the “baby-lung.” The concept isthat the usable lung parenchymal volume is 300-500 ml, that of a6-year-old child. Gattinoni proposed volume control and gentleventilation to maintain the well aeriated lung segment in such settings,noting that higher volumes may be injurious. Unfortunately, this idea ofsaving the baby-lung is unambitious and results in accepting loss oflung capacity for the patient. Instead, the goal of therapy should notbe the maintenance of what remains in a disease state, but theeradication of the disease state.

Nevertheless, the idea of the baby-lung and the ARDS-Net trial of 2000have combined to create a pervasive mindset among ICU providers whichadvocates several ideas implemented concurrently.

First, high PEEP is used to maintain open segments. Since change inpressure yields tidal volume, the result of high PEEP is that, accordingto national clearinghouse practice guidelines, volumes must be limitedto avoid barotrauma. For example, if a ΔP of 20 cm H₂O is required for avolume of 600 ml, and the PEEP is set to 18, then the PIP would be 38for that volume which is in the range known to cause trauma.

Secondly, since lung volume must be lower and CO₂ still needs to beeliminated, ventilatory rates must be increased. When inspiratory cycletime decreases, so do inspiratory phase durations assuming a physiologicI:E ratio. When inspiratory phases are shorter, flow increases and theresult to an atelectatic lung is a regional over distension. Gattinoniacquiesces and argues for permissive hypercapnia, which has the sequelaeof acidosis, and is therefore also undesirable. Nor did Kallet, (R.2018) find any increase in efficacy between low PEEP and recruitmentmaneuvers in a study of over 1,000 patients with ARDS.

Some practitioners, such as Dr. Nader Habashi, have opted instead fortime-cycled pressure limited pressure driven modes of ventilation suchas airway pressure release ventilation (APRV) with long inspiratoryphases and no set PEEP. Additionally, expiratory durations are so shortthat very little volume can escape before the next breath, with theresultant residual volume providing PEEP. The hope is that this willcause a morehomogenous gas distribution, better CO₂ elimination, lessregional overdistension related volutrauma, less barotrauma, and morerecruitment and less atelectrauma. These methods may show promise, buthave not solved these issues.

Other attempts have included high frequency oscillating ventilation(HFOV) and jet ventilation. The former uses tidal volumes so small thatrespiratory rates are measured in Hertz, but expiratory phases, arestill required, and mean pressures remain high with natural flowsdiscarded in favor of mechanisms which essentially “bounce” moleculesalong in the airway. “in the adult,” (HFOV) “uses breathing frequenciesof 180-900 breaths/min (3-15 Hz) with resulting small VT, often lessthan anatomic dead space” . . . “Similar to conventional ventilation,inspired oxygen can travel as a bulk flow and reach proximal alveoli.Longitudinal dispersion occurs by combined convective flow anddiffusion.” . . . “in subjects with moderate ARDS. There was nosignificant improvement in the PaO₂/FIO₂ at 12 h in the supine HFOV arm,whereas both the prone conventional ventilation and prone HFOV groupsshowed a significant improvement” (Nguyen et al, 2016). A significantlimitation of the mode is that it “requires synchrony with anyexistingpatient breathing efforts. Spontaneous respiration results in areduced airway pressure thatthe ventilator may interpret as a circuitdisconnect, subsequently stopping ventilation.” (Papazian et al, 2005).This feature makes ventilator wean hard and often requires significantsedation and paralytic drugs. Therefore, while HFOV offers theoreticalbenefits it is not a panacea at the level of daily clinical praxis.

Jet ventilation, is another manifestation of sequential tidalventilation (breathe in: breathe out). This is typically accomplishedthrough a 14-gauge (ga) catheter, outer diameter (OD) 2.1 mm, internaldiameter (ID) ˜2 mm, allows flow rates of approx. 250 ml/min, andthough, through the use of high inspiratory pressures hypercapnia andresultant acidosis can be avoided readily for periods of 15 min atleast, though at a pressure of 45 psi (Wardet al, 1991). However, in a50-600 min experiment on 25 kg pigs showed that with jet ventilation,“Oxygenation and ventilation were acceptable for 4 mm ID or more, buthypercapnia occurred with the 2 mm stent” (Sütterlin et al, 2015).Indeed, the current use of this invasive technology is such that it'shard to find examples in literature in the past 20 years with durationsof adult human ventilation beyond those required for procedures such asintubation in the setting of airway obstruction and ventilation duringbronchoscopy. Neither procedure typically exceeds 15 min in duration.Therefore, though it bears a superficial resemblance to a single elementof the disclosed invention, in that narrow tubing is used, jetventilation can't be considered a serious long-term plan for mechanicalventilation in the ICU setting.

However, even with APRV, a limiting factor exists to recruitment, thatis, the need to exhale. Humans have a single lumen trachea and rely ontidal flow, so air must escape the way it comes in or the person mustretain CO₂ and eventually die of acidosis. Only extracorporealmembranous oxygenation (ECMO) allows for CO₂ removal without anexpiratory phase as this is effectively heart-lung bypass, andcardiopulmonary bypass, which results in mechanical destruction of redblood cells as they are circulated outside the patient. ECMO use isassociated with a high mortality rate and considered a last-ditchtherapy. If a mode of ventilation could be found which allowed forcontinuous recruitment and CO₂ elimination to normal levels, it wouldtheoretically surpass the utility of most existing modes in the settingof restrictive lung diseases among intubated patients.

As conceived, the disclosed invention will be used in both the ICU andsurgical settings where ventilating a patient is needed. Importantly, aventilator mode which allows the lungs to remain still is very valuablein a thoracic surgery. Surgeons can work more freely and safely whilealso allowing an early warning if sedation wanes, since the patient'sdiaphragm will move before peripheral nerve stimulation. This revealsthat sedation is wearing off. Therefore, the thoracic surgery setting isan important application space for the dual lumen, continuous flowairway design.

A ventilator system which allows for continuous inspiration andintermittent—concurrent expiration, such that the lungs are kept at nearmaximum safe inflation and CO₂ is eliminated to normal levels, wouldmake continuous recruitment possible. Such a system needs to haveseparate inflow and outflow tubes which will divide the native airwayfor this purpose. The system, owing to an effectively continuous,uninterrupted, prolonged, constant, or nearly infinite inspiratoryphase, can be a low-flow system and thus be lung-protective andpro-recruitment in the setting of, or for the prevention of, ARDS. Sincethere will always be air within the lung it is unlikely that additionalPEEP will be required, mean pressures will approach PIPs thus overcomingcritical opening pressures, and pressure readings will be displayed onthe ventilator. Homogenous gas distribution will allow optimal CO₂elimination per unit volume.

Further optimizations include flow titration based on real time feedbackfrom expired CO₂ sensors, possibly also featuring a capnographicwaveform display, inline, and a pressure limiting valve trigger forexpiration in the event that only low pressures are needed forventilation. Thus, when a set pressure was reached due to air buildup,allowing the expiratory tube to open within the ventilator, and airwould flow out until a lower set pressure was reached and noted byonboard systems. In the setting of less compliant lungs requiring higherpressures, the threshold, set by the operator, could be low, allowingfor the valve to remain open continuously and simultaneous inspirationand expiration with flow sufficient to fully aerate would occur, butbarotrauma would be nearly impossible to inflict.

Since there would be easy outflow of air, both apneic and spontaneouslybreathing patients could be placed in this mode with the expectationthat patents could imitate additional expiration from diaphragmaticcontraction at any point and would therefore not have to “fight thevent” as has been a problem in some modes wherein the breaths are timed.

Macro-Static Ventilation

The counterintuitive nature of a ventilation model without tidal breathsin apneic humans should be addressed. Since the airflow is continuousthe flow rates are very low relative to what is found in normalspontaneous ventilation, this combines with concurrent venting foroutflow to yield the gross appearance that the lungs do not move. CO₂ inthis model is offloaded, such as though convective flow. As avisualization exercise, it may be helpful to think of a convection ovenand the unidirectional air flow through a grasshopper. Here instead of acephalad to caudal route for such flow, as in a grasshopper, it is aninspiratory to expiratory tube flow pattern with the middle of thatpattern, the convection oven, being the lungs. Another image that mayhelp normalize this maco-static ventilation mode is that of analogy witha continuous-flow total artificial heart (CFTAH). With a CFTAH in placeblood flow is not pulsatile, so the patient lacks a heartbeat, yetcardiac output, or flow per minute, is maintained in normal ranges. Gasflow through the lungs will be similar in apneic patients thoughadditional tidal flow variation superimposed on the continuous flow modeby a spontaneously breathing patient is not prohibited.

Proof of Concept Porcine Lung Experiment

A new experimental round was undertaken using a single set of ex-vivoporcine lungs approx. 10 hrs. postmortem (preserved on ice in a standardcooler for approx. 8 hrs. prior to use) that were passively ventilated,but not perfused, on each of two systems. The voids within the proximalend of the ET tube were filled with pipe cleaners, circumferentialcompression clamps were applied external to the ET Tube wall, and theend of the ET Tube caulked with a silicone sealant to minimize leakage.The lungs did have a small (less than 2 cm) laceration on the posteriorsurface of the right lower lobe (RLL) and a Vaseline-gauze was appliedthereto. There were also pre-experimental areas on the medial aspect ofthe left lower lobe (LLL) which resembled blebs, but which did notexpand significantly with ventilation.

A tie was placed around the airway superior (cephalad) to the inflatedET tube balloon as the airway was quite large and leakage around thetube had to be controlled for. At no point was the liter flow permin >8, and no flow >5 L/min was used for any purpose other than initialrecruitment from a flaccid and deflated baseline. Neither a bag valvemask nor any PEEP valve was ever employed. Between the 02 tank and theinspiratory tube was a standard 7 ft oxygen tube, and another similartube was attached to the expiratory tube and then in sequence, to apressure gauge and a hand-held flow meter. No sealant was used at thesejoints. 8.5 mm ID ET Tubes were used to accommodate the dual lumenmodel. Videos and still images were obtained to document theexperimental picture and readings on the above devices.

Build 1: Inspiratory and Expiratory tubes of the same diameter: 4.318 mmID

-   -   Recruited with 8 L/min max flow    -   Resting state: 5 L/min Flow in    -   Measured Exp Flow: 4-4.5 L/min    -   Exp Tube Pressure: 27.5 cm H₂O

Build 2: Inspiratory Tube 2.3815 mm ID, Expiratory tube 4.318 mm ID

-   -   Recruited with 5 L/min max flow    -   Resting state: 4 L/min Flow in    -   Measured Exp Flow: 3-4 L/min    -   Exp Tube Pressure: 22.1 cm H₂O

As this was a non-perfused model, products of metabolism, respiration,and the clearance of CO₂ as would normally be shown by arterial bloodgas or end tidal carbon dioxide (ETCO₂) were unavailable.

Findings and Conclusions

Since a normal respiratory rate in adults is 12-20 breaths per minute,traditional physiologic vent settings might include a rate as low as12/min (cycle time 5 sec) with a volume of 500 ml/vent breath being acommon volume for patients who are not exceedingly tall. At a 1:2 I:Eratio this would equate to an inspiratory flow rate of 312.5 ml/sec.With build 1 in the macro static model, so named as the lungs appearmotionless to the untrained eye during continuous ventilation withconvective flow, even when using a recruitment flow of 8 L/min, the flowwas 133 ml/sec since 8,000 ml are delivered evenly over 60 seconds(8,000/60=133.3). Once recruitment was achieved, the flow was dropped toa flow of 5 L/min or 83.3 ml/sec. In build 2 the flow rate of 4 L/minwas 66.6 ml/sec. In some instances, low flow rates may comprise 30-350ml/sec or 80-200 ml/sec. These much lower flow rates should promoteoptimized CO₂ clearance vs. tradition physiologic I: E tidalventilation. The low flow rates:

-   -   1) avoid regional over distension of function lung units;    -   2) promote homogeneity of gas distribution, per APRV practice;    -   3) provide expiratory pressures in the known safe range; and    -   4) provide gentle and continuous recruitment of the lung.

In order to be placed on a ventilator, a patient is intubated. Thismeans having an endotracheal tube placed in the mouth (or nose) andthreaded down into the airway as shown in FIG. 3 . The endotracheal tubehas a small inflatable cuff which is inflated to hold the tube in placeand to seal off any outflow of air around the tube. Thus, the innerlumen of the tube becomes the only path for airflow in and out of thelungs. A ventilator is attached to the tube and ventilates the patient.When a patient is on a ventilator, medication is often given to sedatethe patient. The reason for this is because it can be upsetting anddisturbing to the patient to have an endotracheal tube in place and feelthe ventilator pushing air into the lungs.

Weaning is the process of removing a patient from the ventilator. Mostsurgery patients are removed from the ventilator quickly and easily. Anasal oxygen supply (or mask) often makes the process easier.

Depending on a given patient's pathology and care plan he or she may bequickly removed from mechanical ventilation, while others patients withdiffering pathology and treatment needs will require a longer weaningprocess. In the latter case the ventilator is adjusted to slowly weanthe patient from the ventilator. This may take days or even weeks,gradually allowing the patient to improve their breathing.

A typical ventilator has several modes of operation. CPAP mode, orcontinuous positive airway pressure, is a ventilator setting in whichthe patient initiates the breath, but then the ventilator helps bypushing more air in than the patient would draw in by themselves. Thismakes each breath easier than it would be without ventilator support.Other modes are utilized as already mentioned.

Some patients who are on the ventilator for an extended period of timemay be on CPAP during the day, will full ventilator support at night sothey can fully rest and continue to heal without being exhausted by thework of breathing.

Based on examples in nature, a mode of ventilation that featuressimultaneous inspiration and expiration is achieved by offeringconcurrent inspiration and expiration using periodic expiratory valvetriggers. The triggers include ETCO₂ levels and peak inspiratorypressure (PIP) thresholds. When coupled with an innovative supplementaldual lumen airway, using the native endotracheal tube, continuousinspiration and exhalation is possible without themed to “breathe in andout” separately. This provides a gentle, safe, and continuousventilation by keeping the lungs open and well aerated, and avoidshypercapnia and resultant acidosis as well as atelectasis.

The term inspiratory air, or air flow, means air or other gas mixturesthat is enriched by oxygen that is given to a patient in ventilatorsituations, and may be additionally enriched by other additives such asmedication. Similarly, the term expiratory air or air flow, means theinspiratory air after it leaves a patient's lungs. General use of theterm air or air flow means the gas may be atmospheric, inspiratory, orexpiratory air, depending upon the context. The use of the word lumen iscommon in the art, and refers to an airflow passageway, usually inside aflexible tube, most often round. The use of the word tube in thisapplication means a physical tube, and includes the airway (or lumen)through it. The use of inspiratory line and expiratory line means aconnectable inspiratory tube and connectable expiratory tuberespectively.

FIG. 1 shows a simplified drawing of an endotracheal tube assembly, aleft and right lung 104 a, 104 b, respectively, and lung bronchus 105.The inspiratory tube (or lumen) 102 a sends airflow into an inspiratoryairway channel (or lumen) 102 b which flows down to where the primary(left and right) bronchus airways separate. Air flows out of theinspirator tube and into the lungs in continuous fashion, with modulatedpressure changes. The air flows into the rest of the bronchus 105airways and into the lung alveoli 106 as this represents the path ofleast resistance to gas flow. The inner expiratory tube (or lumen) 103receives the expiratory airflow based being a low pressure relative tothe lungs when the expiratory valve is open and is furthercontrolled/monitored as illustrated in FIG. 4B. An inflatable cuff 101seals off the airflow around the endotracheal tube to prevent air leaks.FIG. 3 better illustrates the endotracheal tube.

The left primary bronchus and right primary bronchus join at thetracheal carina 112. The expiratory tube 103 end is located at adistance 111 of 2-4 cm superior to and in a cranial direction from thetracheal carina. The expiratory tube 103 extends 110 about 2 cm beyondthe end of inspiratory airway channel 102 b (or 4-6 cm superior to thetracheal carina). The inspiratory airway channel is the length andvolume of the endotracheal tube that is not occupied by any other tube,such as the space adjacent the expiratory tube. These positions areimportant for creating a well ventilating lung.

FIGS. 2A-2B show cross sections of FIG. 1 endotracheal tube. A cuff 101is filled with air to seal the air flow around the endotracheal tube,and prevent gas from leaking around it. Cuffs are well known in the artof endotracheal tubes. An approximate position for the expiratory tube103 and inspiratory airway channel 102 b is shown. The inspiratoryairway channel 102 b is the area around the expiratory tube. In FIG. 2B,the inspiratory tube 102 a is shown, which feeds inspiratory flow intothe inspiratory airway channel.

FIG. 3A shows the inspiratory/expiratory tubes of FIG. 1A-1B which arelocated in the patient's endotracheal tube which is placed in thepatient's airway. The Tongue 301, Epiglottis 302, trachea 304, andEsophagus 303 are labeled for anatomical orientation. The inspiratorytube 102 a is located inside the inspiratory airway channel 102 b andconveys inspiratory airflow into the inspiratory airway channel. Aninspiratory tube connector 310 connects the inspiratory tube, and aseparate connector 309 connects the expiratory tube 103. The inspiratorytube is connected to the inspiratory airway channel by use of an endconnector 311 which seals the end of the inspiratory airway channel. Theinflatable cuff 101 is shown. The view at line 3-3 is shown in FIGS.3B-3E for a variety of inspiration/expiration tube arrangements.

The outer endotracheal tube (or airway tube) 312 for the inspiratoryairway channel 102 b must already be in place when the patient isconnected to a ventilator that operates according to the methods of theembodied invention. The outer tube could be a single lumen(endotracheal) airway that is used for other types of common ventilatorssuch as used in emergency response operations. In this case, the innerexpiratory tube 103 along with the inspiratory tube are inserted intothe single lumen tube and the flows to and from the patient areconnected to the embodied invention.

Tube markings are used for positioning the expiratory tube inside theendotracheal tube. This allows the clinical staff the ability tocorrectly position the tubes where they are the most effective. Anendotracheal tube cuff 101 is inflated when the endotracheal tube ispositioned. The cuff is normally inflated by a pressurizing syringe andconnecting tube (not shown).

Alternately, a tracheostomy tube from a surgical tracheostomy procedurecould equally bemused for ventilating a patient if medically needed. Itwould have the same operative control as an endotracheal tube.

FIGS. 3B-3E are examples of routing the inspiratory and expiratory flowsthrough the outer endotracheal tube 312 at line 3-3. In FIG. 3B, theinspiratory tube 320 and the expiratory tube 323 are shown. Anadditional array of inspiratory tubes 321 are optionally added. Thenumber of added inspiratory tubes is flexible.

In FIG. 3C, an alternate expiratory tube 324 is shown with a pair ofpartial circle shapes 325 for the inspiratory tubes. In FIG. 3D, theinspiratory 326/expiratory 327 tube shape is a split circle for a 40-60%ratio. Similarly, in FIG. 3E, the inspiratory 328/expiratory 329 shapeis a modified split circle.

FIGS. 3F-3H are exemplary end connectors for the inspiratory/expiratoryairway shapes through the endotracheal tube. FIG. 3F is a connector asshown in FIG. 3A. An inspiratory tube 330 a, 330 b passes through theconnector 332 which caps and seals the end of the endotracheal tube. Anexpiratory tube hole 331 allows the expiratory tube to pass through theconnector.

FIG. 3G is an alternate connector with a side inspiratory connector 333and also has an expiratory tube hole 334. This connector is adaptablefor the expiratory—inspiratory tube shapes such as shown in FIG. 3C.

FIG. 3H is an alternate connector with two connections 335, 336 for theinspiratory line and the expiratory line. This connector is adaptablefor the expiratory/inspiratory shapes as shown in FIGS. 3D and 3E.

The exemplary inspiratory/expiratory tube shapes shown in FIGS. 3B-3Eare non-limiting examples, and other connectors are possible. Sealingmethods when connecting tubes to prevent leakage is done by methodsknown in the art of tubing connectors.

FIG. 3I shows an alternate embodiment where a tracheostomy tube from atracheostomy procedure is adapted for ventilation control according tothe disclosed invention. Similar to FIG. 3A, an expiratory tube 346 isplaced inside a tracheostomy tube 347 (or airway tube) previouslyinstalled during a surgical procedure. A cuff 348 is used to seal thepatient's trachea. The expiratory tube 346 is connected to an expiratoryline 342 using a connector 341. An inspiratory line 344 is connected toan inspiratory feed 345 by an inspiratory connector 343. The inspiratoryconnector 340 seals the end of the tracheostomy tube 347, and directsthe inspiratory flow into the airway 349 between the tracheostomy tube347 and the expiratory tube 346. The trachea 351 and esophagus 350 arelabeled for anatomical orientation.

In FIG. 4A, a typical control station is a mobile cart 401 with all thecontrols needed to regulate the oxygen and breathing pattern for thepatient. Typically, the cart plugs in to the hospital power, and willcontrol independently. It also has a battery for mobile use, and may,e.g., have sufficient batter power for at least two hours of mobileoperation.

The air/oxygen/medication supply typically has two or more gas modules,one for air and one for O₂. Gases are supplied by a medical pipelinesystem, a compressor, or by gas tanks 409 (illustrated) with a pressureregulating valve 410. Internal to the mobile cart, the oxygen containinggas for the patient is mixed to specific ratios to supply the correctoxygen amount per breath. Other gases may be mixed in such as nitricoxide (NO) to stent open alveoli and prevent atelectasis.

FIG. 4B shows a generalization of the airway system used for inspirationflow and pressure as well as monitoring the expiration flow. A controlpanel 402, with associated computerized controls, monitors the pressureand flows going into the patient. An inspiration flow rate is monitoredby an XY flow sensor 403. The XY sensor provides a combination lungpressure reading X and an air flow reading Y to the microprocessorcontrol unit (MCU) in the control panel. The inspiration air flow isoptionally humidified (not shown) for the patient's comfort. Aninspiratory flow rate sensor 406 monitors the inspiratory air flow tothe patient. The inspiratory line 407 is connected to inspiratory tubeconnector 310 near the patient's mouth, which is routed through theinternal inspiratory tube inside the patent. An expiratory connector 309connects to the expiratory flow line 408.

Two control valves, an inspiratory valve 405 and an expiratory valve404, are controlled by the MCU inside the control panel. Inside thecontrol panel is an oxygen sensor and a CO₂ sensor (not shown) thatmonitors the expiratory flow. The expiratory air vents 411 from thecontrol panel. Alternately, the CO₂ sensor is integrated into a smalldevice that connects directly at the airway, between the breathingcircuit and endotracheal tube.

As seen in FIG. 5 , a typical ventilator operator interface display fora patient is shown. The interface may include one or more of:

-   -   1) A patient ID banner at the top 501;    -   2) Lung pressure graph 502 with instant reading of current value        to right;    -   3) Lung flow graph 503 with instant reading of current value to        right;    -   4) Lung volume tracing charts 504;    -   5) Setpoints for lung control and alarm values 505;    -   6) Various instantaneous readings 506;    -   7) Panel touch-screen control bars for reading units 507; and    -   8) Computer touch-screen control bars to switch to new displays        for alarms, various control pages, information pages, setup        pages, etc. 510.

The computer control is preferably a microprocessor control unit MCUcapable of monitoring all the sensor data, interfacing with the touchdisplay, retaining setpoints, performing control loop and monitoringfunctions, creating alarms, providing external wireless or wiredcommunication with remote sensors, data storage memory, includes anoperating program, and communicates with other computers. The MCU hasvolatile and non-volatile memory to retain operating information andsetpoints, and has needed processing speed and capability to communicatewith displays and operator input. The microcontroller contains one ormore CPUs (computer processor cores) along programmable input/output forperipheral sensors and displays. Preferably program memory in the formof ferroelectric RAM, NOR flash, or OTP ROM, as well as random accessmemory RAM.

Generally, display items on the display screen in FIG. 5 are known inthe art of ventilators, and anesthesia machines, unless noted. The POSAwill recognize that the methods, systems, and devices disclosed hereinmay be advantageously used with both ventilators and anesthesiamachines, as well as with other relevant devices.

Preferably, the operator interface screen utilizes a desirable userinterface, such as a graphical user interface (GUI), which may compriseboth touch sensitivity and a scroll button and allow “clicking” orselecting on highlighted items (or combination of the above). These arethe current industry standard and well known in the art.

In FIGS. 6A-6D show charts for lung pressure, expiratory lung flow rate,and inspiratory flow rate according to the conceived invention when apatient is not breathing on their own. The x-axis for all the charts istime. The lung pressure is in the upper graph and the pressure ismeasured in centimeters of water. The middle graph is expiratory flowrate in ml/sec and the lower graph is the inspiratory flow rate inml/sec. Flow rates are optionally shown in Liters/min.

Pressure Triggered, Pressure Limited, Flow Based Control Mode.

In FIG. 6A, an embodied flow pattern into and out of the lung is shownwhen a patient is not breathing on their own, and a lung pressure cycleis regulated by a ventilator. When using this ventilator control, thelung pressure is maintained between a low pressure setpoint or minimumpressure setpoint 601 and a high pressure setpoint or maximum pressuresetpoint 603. The low pressure setpoint 601 may desirably be in a rangeof 3-35 centimeters of H₂O or in a range of 3-20 centimeters of H₂O. Thehigh pressure setpoint 603 may desirably be in a range of 8-55centimeters of H₂O or in a range of 25-40 centimeters of H₂O. In someinstances, a difference in pressure between the a low pressure setpoint601 and the high pressure setpoint 603 may be in a range of 3-35centimeters of H₂O or 3-20 centimeters of H₂O. The inspiratory flow ratemay be held at a constant 605 setpoint and at an amount that willinflate the lung over time. Additionally, the flow rate is dependentupon a number factors that are discussed in section ‘preferredsetpoints’. When there is a minimum inspiratory flow rate, and a zeroexpiratory flow rate, the lung pressure will rise as shown in the uppergraph.

-   -   a) At time 602, when the lung pressure reaches the high pressure        setpoint 603, an expiratory flow is triggered, and causes the        expiratory control valve to open. The lung pressure then peaks        slightly above the high pressure setpoint, and then declines.        The expiratory flow rises to a peak and then declines back to        zero. The inspiratory flow is held constant at the inspiratory        normal flow setpoint 605.    -   b) At time 604, the lung pressure has lowered to the minimum        setpoint level 601 and this causes the ventilator control to        close the expiratory flow valve. The inspiratory flow is held        constant at the inspiratory normal flow setpoint 605. The lung        pressure then rises. Since the lung is maintained at a minimum        pressure, the lung does not significantly inflate or deflate        during the control cycle.    -   c) At times 606 and 608, the same control is repeated.

The control continues to repeat and provides both ventilating air andpressure recruitment of the lung until the operator changes the controlor disconnects the patient from the ventilator.

Spontaneous Breath Control Modification.

FIG. 6B shows ventilator lung pressure and flow control when the patientinitiates a spontaneous breath cycle by moving their diaphragm. Themovement may be initiated consciously or unconsciously.

-   -   a) For the time between 620 a and 620 b, a spontaneous breath        desire occurs—the lung pressure drops due to a patient        diaphragmatic contraction within a short time.    -   b) At time 620 b, the lung pressure drop 621 is high enough        (about 2 cm H₂O less than 3 seconds) for the controller to        recognize a ‘spontaneous breath’ while the expiratory control        valve is closed. The pressure drop causes the inspiration        flowrate to increase to the high inspiration flow setpoint 631.        The lung pressure rises due to increased inspiration flow. The        expiration control valve is still closed.    -   c) At time 622, the lung pressure rises to a ‘spontaneous breath        complete’ high pressure setpoint 623. This causes the        inspiration flow rate to be reduced to a normal flow setpoint        633. The lung pressure plateaus as the lung enlarges and then        the pressure increases.    -   d) At time 624, the lung pressure reaches a high pressure        setpoint 625. This causes the expiration control valve to open        and the expiration flow rises and falls. The lung pressure        drops. The inspiration flow continues at a constant flow rate.    -   e) At time 626, the low lung pressure setpoint 627 is reached,        causing the expiration valve to close. The inspiration flow        continues at the normal flow setpoint. The lung pressure rises        again due to inspiration flow without expiration flow. In this        case, no additional ‘spontaneous breath’ occurs.    -   f) At time 628, the lung pressure rises to the high pressure        setpoint 625. This causes the expiration valve to open and the        lung pressure falls.

Typically, control continues utilizing the pressure triggered, pressurelimited, flow base control previously described if no additionalspontaneous breaths occur.

De-Recruiting Control Modification.

In FIG. 6C, the lung pressure and flows are shown for a patient during ade-recruiting event. That is, the lung pressure is unregulated for ashort time, and the lung is allowed to significantly deflate. Typicalsituations for this include:

-   -   a) When a patient is moved from one hospital unit to another and        needs to be switched to from a portable ventilator to a        stationary ventilator.    -   b) When a patient is brought in by an emergency response team,        and the patient needs to be switched from a portable ‘bag type’        ventilator to a hospital ventilator. In this case, the patient        will also be intubated.    -   c) During surgery when collapsed lungs allows better surgical        access.    -   d) When a camera is deployed into the airway of a patient.    -   e) For a lung treatment, such as flushing by sterile salt water        (saline) or with instillation of other liquid medicines.    -   f) For deploying suction equipment into the patient's airway.

For the de-recruiting event such as moving the patient, the lung vitalsare shown in FIG. 6C. The patient that is briefly disconnected from aprevious ventilator control and re-connected to a ventilator controlaccording to an embodiment of the invention.

-   -   a) Between times 640 and 642, when reconnecting the patient and        turning on the ventilator, the lung pressure falls, and the        expiratory flow drops toward zero as the patient exhales their        reserve of air while there is no connected ventilator circuit.        The pressure and expiratory flow are shown in dot dash lines.    -   b) At time 642, the patient is connected to the ventilator and        the operator presses a start button to activate the control        setpoints—low pressure 641, high pressure 643, inspiratory low        flow 645 and inspiratory high flow 647. At this time, the lung        pressure is below the low pressure setpoint 641, and this causes        the expiratory valve to close. This also causes the inspiratory        valve to open and move to the high flow rate control setpoint        647. The lung fills quickly and the pressure quickly ramps up        due to the high amount of flow into the lung.    -   c) At time 644, the lung pressure reaches the high lung pressure        setpoint 643. This causes the inspiratory flow to ramp down to        the normal flow rate 645 setpoint. It also causes the expiratory        valve to open. The expiratory flow rises and falls.    -   d) At time 646, the lung pressure reaches the low pressure        setpoint 641 and this causes the expiratory valve to close. The        constant inspiratory flow continues. The lung pressure rises.    -   e) At time 648, the lung pressure reaches the high pressure        setpoint 643. This causes the expiratory valve to open.

Typically, control continues utilizing the pressure triggered, pressurelimited, flow based control previously described.

Preferably, the high inspiratory flow rate 647 in FIG. 6C is the same asthe high inspiratory flow rate setpoint 631 in FIG. 6B, but it is not arequirement. Similarly, the low inspiratory flow rate 645 in FIG. 6C isthe same as the low inspiratory flow rate setpoint 633 in FIG. 6B, butit is not a requirement.

ETCO₂ Control Modification.

FIG. 6D shows a control using ETCO₂ as an expiratory control option inaddition to the pressure triggered, pressure limited, flow basedcontrol. Over time, the amount of CO₂ may build up in a patient if thereis insufficient expiratory volume over time. The CO₂ builds up in thebody and needs to be ‘offloaded.’ Importantly, an ETCO₂ measurement isonly possible during expiratory flow, as the CO₂ sensor is located inthe expiratory line. To this end, a small amount of expiratory flow isadded to the control based on an expiratory flow setpoint 657.

In this case, a high ETCO₂ setpoint 655 is added to the control. Whenthe setpoint is reached, the expiratory valve, which is slightly open toallow ETCO₂ readings, opens fully and the lungs will be allowed todeflate in order to offload CO₂,

As seen in the ventilatory control of FIG. 6D, when the ETCO₂ is highenough, it will cause the expiratory flow to change.

-   -   a) At time 652, the lung pressure begins to rise, the ETCO₂ is        rising, and a relatively small amount of expiratory flow occurs        according to expiratory flow setpoint 657. The inspiratory flow        is at an inspiratory flow setpoint 659.    -   b) At time 654, the high pressure setpoint 651 has been reached,        and this causes the expiratory valve to open. The lung pressure        falls. It is noted that the ETCO₂ amount is near the high ETCO₂        setpoint 655, but has not been exceeded.    -   c) At time 656, the lung pressure is at the low pressure        setpoint 653, and this causes the expiratory flow to drop to the        expiratory flow setpoint 657. The lung pressure rises because        the inspiratory flow rate is higher than the expiratory flow        rate.    -   d) At time 658, the ETCO₂ amount is at the high ETCO₂ setpoint        655 and this causes the expiratory valve to open. The valve        stays open and allows the lung pressure to decline to near zero        as the lung low pressure setpoint 653 is temporarily suspended.        The lung is allowed to deflate, as seen by the long expiratory        flow, in order to offload CO₂. The loss of volume and pressure        are side effects of the fact that CO₂ is part of the air        mixture, so air mixture must be blown out. The reason for        opening the expiratory valve is not about lowering pressure, it        is about lowering CO₂.    -   e) At time 660, and the expiratory flow setpoint amount 657 is        activated due to the decline in ETCO₂. This causes the        expiratory flow to decline to the setpoint amount. The lung        pressure rises. The time between times 660 and 662 is long        enough to allow the lungs to re-inflate and pressurize.    -   f) At time 662, the high pressure setpoint 651 has been reached,        and this causes the expiratory valve to open. The lung pressure        falls.    -   g) The control continues with periodic increases in expiratory        flow based on either the high lung pressure or high ETCO₂        measurements.

Typically, the pressure control continues as the primary control withpotential periodic interruptions due to any high ETCO₂ measurements.Importantly, if there are too many interruptions, the inspiratory orexpiratory setpoints should be modified. ETCO₂ measurements may bedetected by an ETCO₂ sensor disposed within the expiratory line, orcoupled to the expiratory tube. Because obtaining readings from an ETCO₂sensor conventionally requires flow, in the systems and methodsdescribed herein, a closed expiatory control valve or a closed expiatoryline as understood by a POSA may comprise a substantially closedexpiatory control valve or a closed expiatory line that allows for somenominal, de minimus, reduced, or minimum flow which allows for the ETCO₂sensor to obtain readings.

The inspiratory flow is maintained at a constant level, but at a higheramount than the inspiratory flow setpoint 609 in FIG. 6A to compensatefor the constant small expiratory flow of 657.

Overall, the periodic lung cycle in FIG. 6D may be longer than in FIG.6A, primarily due to the lungs being allowed to inflate and deflate to asignificant degree.

Per medical direction, a patient may be transitioned from the lungcycles shown in FIG. 6A to those shown in FIG. 6D which are inclusive ofthe FIG. 6A ventilator control, and also include the ETCO₂ trigger. At alater time, the patient may be switched back to the FIG. 6A controlmode, and no longer utilize the ETCO₂ sensor and control of FIG. 6D.

However, if a spontaneous breath event occurs (pressure drop setpointexceeded), the ETCO₂ control is superseded by the spontaneous breathcontrol. In this case, the expiratory valve closes and the inspiratoryvalve is opened to the high flow setpoint 632 as shown in FIG. 6B attime 620 b. Then the spontaneous breath control continues until time628. Then the control is shifted back to ETCO₂ control.

For comparison to FIG. 6D, FIG. 7 shows a typical Capnographic Waveformfor a typical breathing patient. This is the ETCO₂ readout from a CO₂sensor in the expiration flow. The inspiration amount 701 is near zeroas air goes into the lungs. The expiration amount of ETCO₂ 702 is shownand it slightly increases during lung exhale as the exchange of O₂ andCO₂ continues during the exhale period of the patent. The currentreading ETCO₂ 703 is shown to the right of the chart for highvisibility. A typical ETCO₂ reading is between 35-45 mm Hg. The higherwaveform reading 702 is important for doctors, as it is an importantnumber for understanding how well the lungs are functioning as O₂—CO₂exchangers, and can indicate states of bronchospasm and other diseasestates.

Preferred Setpoints

Humans breathe in a tidal volume of air in a single breath. A breath isdivided into inspiratory flow (inhale) and expiratory flow (exhale). Intidal ventilation the tidal volume must be delivered over the totalinspiratory time frame for patient breathing to be normal. Theexpiratory flow occurs over a longer time at a inspiratory/expiratoryratio of about 1:2. For example: a tidal volume of 600 ml per breath atthe rate of 20 breaths/min gives an average inspiratory volume rate of0.6 L×20 breath/min=12 L/min. However, the flowrate during inspiration(only) is three times the average flow. This is typical for aphysiologically normal person with a 20/40 second inspiration/expirationtime per minute.

Conversely, a continuously flowing inspiration will deliver 12L oversixty seconds at a constant flow of 0.2 L/sec during an entire minute,without simulating a patient's breath.

An operator is able to set the volume flow rate in L/min or ml/min. Theresult of either set variable will be the calculation and display ofboth (to two significant digits).

Preferably, to determine the amount of flow the patient needs, theoperator inputs the patient's biological sex and height and softwarecalculates Ideal body weight (IBW) via the Devine formula:

-   -   1. Man: Ideal Body Weight (kg)=50+2.3 kg per inch over 5 feet.    -   2. Woman: Ideal Body Weight (kg)=45.5+2.3 kg per inch over 5        feet.

In constant flow operators set a “rate and volume” for vent flow ratewhich is based on IBW. Even though the flow (in/out) to the lungs iscontinuous, it is operator friendly to show the setpoints in rate andvolume/breath, similar to typical ventilator breathing modes:

-   -   Rate: 15 breaths/min    -   Volume/breath: 8 ml/kg IBW

For example: a 70″ male patient with an IBW of 73 kg, and a chosensetpoint rate of 15 breaths/min will be:

-   -   Volume/breath: 73 kg*8 ml/kg=584 ml/breath    -   Volume/min: 0.584 L*15=8.76 L/min

Preferably, the volume rate in both minutes and seconds are both shown,that is, 8.76 L/min and 146 ml/sec (i.e. 8760 ml/min/60). Since flowrate mode is continuous, the actual flowrate is a constant 8.76 L/minover the entire minute.

As another example, the operator sets the rate and volume independent ofIBW: (e.g. rate 12 breaths/min, volume 500 ml/breath, which would be avolume display of 6 L/min and 100 ml/sec.

Both the rate and the volume are important to ventilator operators. Theoperator receives feedback of ventilating progress by monitoring thepatient's oxygen level from a suitable patient blood oxygen readout onan operator display. Additionally, the amount of CO₂ in the expiratoryflow is important to understand how well the lung functions by theexchange rate of oxygen into the blood.

In a preferred embodiment, the lung is set up with a minimum continuousinspiratory flowrate. The minimum flow rate (perhaps 100 ml/sec) isregulated by the inspiratory control valve. The operator watches, andadjusts the flow rate, until a desired minimum lung inflation pressureis reached and the ETCO₂ readings are within a normal range. A shown inFIGS. 1A and 2A, the internal flow within the lungs allows theinspiratory air to reach throughout the lungs.

The operation of the lung maintains a steady state condition if theETCO₂, and the cardiovascular system operates within normal parameters.

Trigger setpoints for the expiratory control valve opening include:

-   -   a. Max/Min pressure setpoints. The operator sets an opening        pressure setpoint and a closing pressure setpoint for the        expiratory valve. Exemplary setpoints are opening the valve at        32 cm H₂O and closing the valve at 2 cm H₂O. The expiratory        valve then stays closed until the pressure reaches 32 cm H₂O,        and so on. This creates a breathing pattern for the patient and        is the main trigger method. The amount of flow is regulated by        the inspiratory control valve. An exemplary setpoint is 100        ml/sec.    -   b. Optional Peak End Tidal Carbon Dioxide (ETCO₂) setpoint,        which is used in conjunction with one or more other triggers.        The ETCO₂ is measured by a sensor in the expiratory tube (not        shown).        -   i. Operator sets ETCO₂ Max setpoint (for example, 50 mm Hg).            The expiratory valve remains open until the measured value            is less than the setpoint value. Note: the operator may            change the setpoint value while valve is open or closed and            system will accept new setpoint.    -   c. Expiratory Pause (i.e. manual override by operator) which        opens the expiratory control valve when the pause button is        pushed down, and also closes the inspiratory valve).    -   d. When a maximum time setpoint is reached for an expiratory        flow to happen (i.e. breath to be exhaled), this triggers the        opening of the expiratory valve.

Alarm limits are displayed separately on an alarm screen.

-   -   1. Any value that can be set or measured may be associated with        both high and low alarms.    -   2. Alarms are any of: visual, audio, or both on a per case        basis.    -   3. Alarms are set prior to use and can be changed by the        operator at any time.    -   4. No ventilation starts without setting at least one alarm.    -   5. This mode allows separate alarms when in-line nebulization of        medications are given to the patient. The operator may change        the alarms when the nebulizer is used.

While this disclosure includes a number of embodiments in differentforms, the particular embodiments presented are with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the disclosed structures, devices, methods, andsystems, and is not intended to limit the broad aspect of the disclosedconcepts to the embodiments illustrated. Additionally, it should beunderstood by those of ordinary skill in the art that other structures,manufacturing devices, and examples could be intermixed or substitutedwith those provided. In places where the description above refers toparticular embodiments, it should be readily apparent that a number ofmodifications may be made without departing from the spirit thereof andthat these embodiments and implementations may be applied to othertechnologies as well. Accordingly, the disclosed subject matter isintended to embrace all such alterations, modifications and variationsthat fall within the spirit and scope of the disclosure and theknowledge of one of ordinary skill in the art. As such, it will beevident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the inventions asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1-5. (canceled)
 6. A method of ventilating lungs in breathing andnon-breathing patients, comprising: maintaining an inspiratory flow rateat an inspiratory setpoint at a low flow setting; and regulating lungpressure in a patient between a high pressure setpoint and a lowpressure setpoint with periodic expiratory flows and continuousinspiratory flow by: adjusting an expiratory control valve to an openposition when a lung pressure is at or above a high pressure setpoint,and adjusting an expiratory control valve to a closed position when alung pressure is at or below a low pressure setpoint.
 7. (canceled) 8.The method of claim 6, further comprising providing additional flowthrough the lung in response to a trigger resulting from a patient'sattempt to initiate a spontaneous breath.
 9. The method of claim 8,wherein the trigger for a spontaneous breath comprises a drop ofpressure, or a spontaneous increase of flow, brought about bycontracture of the patient's diaphragm.
 10. The method of claim 8,wherein the trigger for expiratory flow comprises one or more of: (i) anincrease of pressure, (ii) real time continuous ETCO₂ readings in arange of 30-70 mm of mercury (Hg), or (iii) after a defined time delaygreater than 1.5 seconds.
 11. The method of claim 10, wherein thetrigger for expiratory flow comprises readings from an ETCO₂ sensor of30-70 mm of mercury (Hg), wherein the ETCO₂ reading is a real-timeresult produced by constant monitoring with a slight continuousexpiratory flow sufficient for obtaining a reading from the ETCO₂sensor, and wherein the inspiratory flow is upregulated to compensatefor the slight continuous expiratory flow.
 12. The method according toclaim 6, further comprising regulating a spontaneous breath control by:detecting a predetermined pressure drop in lung pressure when theexpiatory control valve is substantially closed; and triggering aninspiratory setpoint cycle after detecting the predetermined pressuredrop by: changing the inspiratory setpoint to a high flow setting toincrease inspiratory flow, and subsequently changing the inspiratorysetpoint to a low flow setting after increasing the inspiratory flowonce lung pressure is at or above a spontaneous breath pressuresetpoint.
 13. The method of claim 6, wherein the low flow settingcomprises a flow in a range of 30-350 ml/second.
 14. (canceled)
 15. Themethod of claim 6, wherein: the high pressure setpoint is within a rangeof 8-55 centimeters of H₂O; and the low pressure setpoint is within arange of 3-35 centimeters of H₂O. 16-18. (canceled)
 19. The method ofclaim 12, wherein the predetermined pressure drop is in a range of 0.5-3centimeters of H₂O for a time in a range of 0.2-4 seconds. 20.(canceled)
 21. The method of claim 6, further comprising: measuring anexpiratory ETCO₂ amount with an ETCO₂ measurement device; furtheropening the expiratory control valve when the expiratory ETCO₂ amount isabove an ETCO₂ high setpoint of 30-70 mm of mercury (Hg) to control theexpiratory flow according to the low flow setting; and substantiallyclosing the expiratory control valve when the ETCO₂ amount is at orbelow an ETCO₂ low setpoint 20-50 mm of mercury (Hg) while the lungpressure is at or below the low pressure set point.
 22. The method ofclaim 21, further comprising at least 5 mm mercury (Hg) offset betweenthe high setpoint and the low setpoint.
 23. A method of ventilatinglungs in breathing and non-breathing patients, comprising: providingcontinuous inspiratory flow to a patient; and providing an intermittentexpiratory flow from the patient while providing the continuousinspiratory flow to facilitate concurrent venting outflow and CO₂offloading from the lung.
 24. The method of claim 23, further comprisingproviding additional flow through the lung in response to a triggerresulting from a patient's attempt to initiate a spontaneous breath. 25.The method of claim 24, wherein the trigger for a spontaneous breathcomprises a drop of pressure, or a spontaneous increase of flow, broughtabout by contracture of the patient's diaphragm.
 26. The method of claim24, wherein the trigger for expiratory flow comprises one or more of:(i) an increase of pressure, (ii) real time continuous ETCO₂ readings ina range of 30-70 mm of mercury (Hg), or (iii) after a defined time delaygreater than 1.5 seconds.
 27. The method according to claim 23, furthercomprising regulating a spontaneous breath control by: detecting apredetermined pressure drop in lung pressure when the expiatory controlvalve is substantially closed; and triggering an inspiratory setpointcycle after detecting the predetermined pressure drop by: changing theinspiratory setpoint to a high flow setting to increase inspiratoryflow, and subsequently changing the inspiratory setpoint to a low flowsetting after increasing the inspiratory flow once lung pressure is ator above a spontaneous breath pressure setpoint.
 28. The method of claim23, wherein the inspiratory flow comprises a low flow setting comprisinga flow in a range of 30-350 ml/second.
 29. The method of claim 23,further comprising regulating lung pressure in a patient between a highpressure setpoint in a range of 8-55 centimeters of H₂O and a lowpressure setpoint in a range of 3-35 centimeters of H₂O.
 30. The methodof claim 27, wherein the predetermined pressure drop is in a range of0.5-3 centimeters of H₂O for a time in a range of 0.2-4 seconds.
 31. Themethod of claim 34, further comprising at least 5 mm mercury (Hg) offsetbetween the high setpoint and the low setpoint.